Unlike other laser boresighting systems that insert into the muzzle of the firearm, these are precisely engineered to fit into the chamber, ensuring exact and consistent laser alignment with the bore. Sighting in your firearm has never been easier. Load the laser into the chamber, place the dot on a target downrange, align your sights crosshairs or dot with the projected spot. Youll be boresighted and ready for live fire fine-tuning. You can also use this handy tool to check your zero after transporting your firearm to the range or hunting ground. Use the handgun versions to practice drawing and getting on target quickly. More than a dozen rifle, handgun and shotgun calibers/bores to choose from. Cancer and Reproductive Harm- www.P65Warnings.ca.gov. Size: 243. Type: Boresighters.